1. Field of the Invention
The present invention relates to a thermoplastic resin composition providing a shaped article having a delustered and pleasing appearance and a good impact resistance.
2. Description of the Related Art
Thermoplastic resins generally have light weight, good moldability and good electrically insulating property. Accordingly, thermoplastic resins are used in the fields of interior trims of automobiles, parts of households electrical applicances and the like. However, these articles have in general a high gloss. To imparted high-quality feeling molded articles having a reduced surface gloss have been proposed, and the demand for these molded articles has been increasing. Moreover, molded articles having a high surface gloss dazzle the user's vision and cause a problem of the safety, and low-gloss molded articles are desired for solving this problem.
As ordinary delustering methods for thermoplastic resins, there are known a method using a mold having the entire surface embossed, a method comprising coating the surface of a molded article with a liquid delustering agent, a method comprising incorporating an inorganic filler into a resin (Japanese Examined Patent Publication No. 49-44582), a method comprising adding a rubbery polymer after the polymerization (Japanese Examined Patent Publication No. 48-24034, Japanese Unexamined Patent Publication No. 54-142259 and Japanese Examined Patent Publication No. 62-59725), a method comprising adding a rubber-modified thermoplastic resin (Japanese Unexamined Patent Publication No. 56-133353, No. 59-89346, No. 60-18536, No. 60-202143 and No. 62-101616), and a method comprising incorporating a three-dimensional resin component formed by using a crosslinking monomer (Japanese Unexamined Patent Publication No. 63-63740).
In the method using a mold having the entire surface embossed, the mold-preparing cost increases and the repair and maintenance of the mold are complicated and troublesome, and no satisfactory delustering effect can be obtained. In the surface coating method, the coating step is expensive and there is a risk of deterioration of the resin surface by the solvent. In the method in which an inorganic filler is incorporated, the mechanical properties, especially the impact strength, are drastically degraded, and the appearance of the molded article becomes poor.
The method comprising adding a rubbery polymer after the polymerization causes reduction of heat resistance or rigidity, and the gloss is not uniformly reduced (uneven gloss). In the method comprising adding a rubber-modified thermoplastic resin, the delustering degree varies according to the molding conditions, and the method comprising adding a three-dimensional resin component formed by using a crosslinking monomer, the molding processability and the appearance of the molded article are poor.
Recently, a styrene resin delustered by introduction of epoxy groups has been proposed. For example, there have been proposed an ABS resin comprising an epoxy group-introduced graft copolymer as a constituent (Japanese Unexamined Patent Publication No. 61-218651), an ABS resin containing an epoxy group-containing copolymer (Japanese Unexamined Patent Publication No. 63-63740), and a delustered resin composition comprising an ABS resin and an epoxy group-containing olefin copolymer (Japanese Unexamined Patent Publication No. 59-89346).
Moreover, a resin composition comprising a rubbery polymer and an ethylenically unsaturated carboxylic acid copolymer which is delustered by incorporation of a metal compound, has been proposed (Japanese Unexamined Patent Publication No. 60-197713).
However, in the resin composition formed by mere introduction of an epoxy group or carboxyl group, the gloss is not satisfactorily reduced and the appearance of the molded article is not good.
Still further, a resin composition comprising polyglutarimide (PGI) and an ABS resin has been proposed (Japanese Unexamined Patent Publication No. 58-83057). This resin composition has excellent impact resistance and heat resistance, but the gloss is high.
Furthermore, there has been proposed a resin composition comprising polyglutarimide, a polymer of an acrylic rubber and an acrylic acid ester, and an ABS resin (U.S. Pat. No. 4,217,424). In this resin composition, the impact resistance of polyglutarimide can be improved, but the gloss is still high.
Still in addition, a resin composition comprising an imidized acrylic resin and a polyamide has been proposed (European Patent 474215, Japanese Unexamined Patent Publication No. 59-25836 and No. 59-117550), but no delustering effect is obtained in this composition.
The present assignee previously proposed a delustered thermoplastic resin composition comprising an ABS resin, a PGI resin and a vinyl type crosslinked copolymer comprising a polyfunctional monomer as a comonomer component (Japanese Unexamined Patent Publication No. 64-48848). The crosslinked copolymer in this composition is a polymer which has been partially crosslinked in advance, and this copolymer has no reactivity with PGI. For this reason or other reason, the composition is still unsatisfactory in surface appearance and impact resistance.
As the polyfunctional monomer, compounds having at least copolymerizable double bonds, preferably two copolymerizable double bonds, for example, non-conjugated divinyl compounds represented by divinylbenzene, diallyl maleate and polyvalent acrylate compounds, are used.